Calling a generator function returns a generator object

src/runtime.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 2274 matching lines @@
   HandleScope scope(isolate);
   ASSERT(args.length() == 2);
   CONVERT_ARG_HANDLE_CHECKED(JSFunction, function, 0);
   CONVERT_SMI_ARG_CHECKED(num, 1);
   RUNTIME_ASSERT(num >= 0);
   SetExpectedNofProperties(function, num);
   return isolate->heap()->undefined_value();
 }
 
 
+RUNTIME_FUNCTION(MaybeObject*, Runtime_CreateJSGeneratorObject) {
+  NoHandleAllocation ha(isolate);
+  ASSERT(args.length() == 0);
+  JavaScriptFrameIterator it(isolate);
+  JavaScriptFrame* frame = it.frame();
+  JSFunction* function = JSFunction::cast(frame->function());
+  RUNTIME_ASSERT(function->shared()->is_generator());
+
+  JSGeneratorObject* generator;
+  if (frame->IsConstructor()) {
+    generator = JSGeneratorObject::cast(frame->receiver());
+  } else {
+    MaybeObject* maybe_generator =
+        isolate->heap()->AllocateJSGeneratorObject(function);
+    if (!maybe_generator->To(&generator)) return maybe_generator;
+  }
+  generator->set_function(function);
+  generator->set_context(isolate->heap()->undefined_value());
+  generator->set_continuation(0);
+  generator->set_operand_stack(isolate->heap()->empty_fixed_array());
+
+  return generator;
+}
+
+
 MUST_USE_RESULT static MaybeObject* CharFromCode(Isolate* isolate,
                                                  Object* char_code) {
   uint32_t code;
   if (char_code->ToArrayIndex(&code)) {
     if (code <= 0xffff) {
       return isolate->heap()->LookupSingleCharacterStringFromCode(code);
     }
   }
   return isolate->heap()->empty_string();
 }
@@ skipping 10779 matching lines @@
     // Handle last resort GC and make sure to allow future allocations
     // to grow the heap without causing GCs (if possible).
     isolate->counters()->gc_last_resort_from_js()->Increment();
     isolate->heap()->CollectAllGarbage(Heap::kNoGCFlags,
                                        "Runtime::PerformGC");
   }
 }
 
 
 } }  // namespace v8::internal